This invention relates to electrical motors in general and more particularly to a commutating device for an electrical motor supplied from a d-c voltage source, which comprises semiconductor switching elements arranged in a bridge circuit which are addressed by a control voltage in dependence on the rotor position.
Such a commutating device is described in U.S. Pat. No. 4,047,081. Because the transistors of this commutating device are connected in a bridge circuit, their bases are at different potentials. It is therefore, necessary to connect the control voltage to the bases of the transistors with the interposition of transformers or to provide several control voltage sources which have no potential relative to each other.
It is an object of the present invention to develop a commutating device of the type described above in which the semiconductor switching elements can be controlled without transformers and without separate control voltage sources.